Metal alloy for a stent

ABSTRACT

A stent that is at least partially formed of a novel metal alloy, which novel metal alloy improves the physical properties of the stent.

The present invention claims priority on U.S. Provisional ApplicationSer. Nos. 60/658,226 filed Mar. 3, 2005 entitled “Improved Metal Alloysfor Medical Devices”; 60/694,881 filed Jun. 29, 2005 entitled “ImprovedMetal Alloys for Medical Devices”; and 60/694,891 filed Jun. 29, 2005entitled “Improved Metal Alloys for Medical Devices”, all of which areincorporated herein by reference.

The invention relates generally to medical devices, and particularly toa medical device that is at least partially formed of a novel metalalloy that includes molybdenum and rhenium and at least metal oftitanium, yttrium, and/or zirconium, and more particularly to a stentthat is at least partially formed of the novel metal alloy and whichstent is useful in treating a body passageway.

BACKGROUND OF THE INVENTION

Medical treatment of various illnesses or diseases commonly includes theuse of one or more medical devices. Two types of medical devices thatare commonly used to repair various types of body passageways are anexpandable graft or stent, or a surgical graft. These devices have beenimplanted in various areas of the mammalian anatomy. One purpose of astent is to open a blocked or partially blocked body passageway. When astent is used in a blood vessel, the stent is used to open the occludedvessel to achieve improved blood flow which is necessary to provide forthe anatomical function of an organ. The procedure of opening a blockedor partially blocked body passageway commonly includes the use of one ormore stents in combination with other medical devices such as, but notlimited to, an introducer sheath, a guiding catheter, a guide wire, anangioplasty balloon, etc.

Various physical attributes of a stent can contribute directly to thesuccess rate of the device. These physical attributes includeradiopacity, hoop strength, radial force, thickness of the metal,dimensions of the metal and the like. Cobalt and chromium alloys andstainless steel are commonly used to form stents. These materials arecommonly used since such materials having a known history of safety,effectiveness and biocompatibility. These materials however have limitedphysical performance characteristics as to size, strength, weight,bendability, biostability and radiopacity.

The present invention can be generally directed to a medical device suchas, but not limited to, a stent that is at least partially formed of anovel metal alloy that improves the physical properties of the medicaldevice thereby improving the success rate of such medical device.

SUMMARY OF THE INVENTION

The present invention is generally directed to a medical device that isat least partially made of a novel metal alloy having improvedproperties as compared to past medical devices. The novel metal alloyused to at least partially form the medical device improves one or moreproperties (e.g., strength, durability, hardness, biostability,bendability, coefficient of friction, radial strength, flexibility,tensile strength, tensile elongation, longitudinal lengthening,stress-strain properties, improved recoil properties, radiopacity, heatsensitivity, biocompatibility, etc.) of such medical device. These oneor more improved physical properties of the novel metal alloy can beachieved in the medical device without having to increase the bulk,volume and/or weight of the medical device, and in some instances theseimproved physical properties can be obtained even when the volume, bulkand/or weight of the medical device is reduced as compared to medicaldevices that are at least partially formed from traditional stainlesssteel or cobalt and chromium alloy materials. The novel metal alloy thatis used to at least partially form the medical device can thus 1)increase the radiopacity of the medical device, 2) increase the radialstrength of the medical device, 3) increase the yield strength and/orultimate tensile strength of the medical device, 4) improve thestress-strain properties of the medical device, 5) improve the crimpingand/or expansion properties of the medical device, 6) improve thebendability and/or flexibility of the medical device, 7) improve thestrength and/or durability of the medical device, 8) increase thehardness of the medical device, 9) improve the longitudinal lengtheningproperties of the medical device, 10) improved the recoil properties ofthe medical device, 11) improve the friction coefficient of the medicaldevice, 12) improve the heat sensitivity properties of the medicaldevice, 13) improve the biostability and/or biocompatibility propertiesof the medical device, and/or 14) enable smaller, thinner and/or lighterweight medical devices to be made. The medical device generally includesone or more materials that impart the desired properties to the medicaldevice so as to withstand the manufacturing processes that are needed toproduce the medical device. These manufacturing processes can include,but are not limited to, laser cutting, etching, crimping, annealing,drawing, pilgering, electroplating, electro-polishing, chemicalpolishing, cleaning, pickling, ion beam deposition or implantation,sputter coating, vacuum deposition, etc.

In one non-limiting aspect of the present invention, a medical devicethat can include the novel metal alloy is a stent for use in a bodypassageway; however, it can be appreciated that other types of medicaldevices could be at least partially formed from the novel metal alloy.As used herein, the term “body passageway” is defined to be anypassageway or cavity in a living organism (e.g., bile duct, bronchioletubes, nasal cavity, blood vessels, heart, esophagus, trachea, stomach,fallopian tube, uterus, ureter, urethra, the intestines, lymphaticvessels, nasal passageways, eustachian tube, acoustic meatus, etc.). Thetechniques employed to deliver the medical device to a treatment areainclude, but are not limited to, angioplasty, vascular anastomoses,interventional procedures, and any combinations thereof. For vascularapplications, the term “body passageway” primarily refers to bloodvessels and chambers in the heart. The stent can be an expandable stentthat is expandable by a balloon and/or other means. The stent can havemany shapes and forms. Such shapes can include, but are not limited to,stents disclosed in U.S. Pat. Nos. 6,206,916 and 6,436,133; and all theprior art cited in these patents. These various designs andconfigurations of stents in such patents are incorporated herein byreference.

In another and/or alternative non-limiting aspect of the presentinvention, the stent is generally designed to include at least about 25weight percent of the novel metal alloy; however, this is not required.In one non-limiting embodiment of the invention, the stent includes atleast about 40 weight percent of the novel metal alloy. In anotherand/or alternative non-limiting embodiment of the invention, the stentincludes at least about 50 weight percent of the novel metal alloy. Instill another and/or alternative non-limiting embodiment of theinvention, the stent includes at least about 60 weight percent of thenovel metal alloy. In yet another and/or alternative non-limitingembodiment of the invention, the stent includes at least about 70 weightpercent of the novel metal alloy. In still yet another and/oralternative non-limiting embodiment of the invention, the stent includesat least about 85 weight percent of the novel metal alloy. In a furtherand/or alternative non-limiting embodiment of the invention, the stentincludes at least about 90 weight percent of the novel metal alloy. Instill a further and/or alternative non-limiting embodiment of theinvention, the stent includes at least about 95 weight percent of thenovel metal alloy. In yet a further and/or alternative non-limitingembodiment of the invention, the stent includes about 100 weight percentof the novel metal alloy.

In still another and/or alternative non-limiting aspect of the presentinvention, the novel metal alloy that is used to form all or part of thestent 1) is not clad, metal sprayed, plated and/or formed (e.g., coldworked, hot worked, etc.) onto another metal, or 2) does not haveanother metal or metal alloy metal sprayed, plated, clad and/or formedonto the novel metal alloy. It will be appreciated that in someapplications, the novel metal alloy of the present invention may beclad, metal sprayed, plated and/or formed onto another metal, or anothermetal or metal alloy may be plated, metal sprayed, clad and/or formedonto the novel metal alloy when forming all or a portion of a stent.

In yet another and/or alternative non-limiting aspect of the presentinvention, the novel metal alloy that is used to form all or a portionof the stent includes a majority weight present rhenium and molybdenum,and also includes at least one additional metal which includes titanium,yttrium, and/or zirconium. The novel alloy can include one or more othermetals such as, but not limited to, calcium, chromium, cobalt, copper,gold, iron, lead, magnesium, nickel, niobium, platinum, rare earthmetals, silver, tantalum, tungsten, zinc, and/or alloys thereof. Theaddition of controlled amounts of titanium, yttrium, and/or zirconium tothe molybdenum and rhenium alloy has been found to form a metal alloythat has improved physical properties over a metal alloy thatprincipally includes molybdenum and rhenium. For instance, the additionof controlled amounts of titanium, yttrium, and/or zirconium to themolybdenum and rhenium alloy can result in 1) an increase in yieldstrength of the alloy as compared to a metal alloy that principallyincludes molybdenum and rhenium, 2) an increase in tensile elongation ofthe alloy as compared to a metal alloy that principally includesmolybdenum and rhenium, 3) an increase in ductility of the alloy ascompared to a metal alloy that principally includes molybdenum andrhenium, 4) a reduction in grain size of the alloy as compared to ametal alloy that principally includes molybdenum and rhenium, 5) areduction in the amount of free carbon, oxygen and/or nitrogen in thealloy as compared to a metal alloy that principally includes molybdenumand rhenium, and/or 6) a reduction in the tendency of the alloy to formmicro-cracks during the forming of the alloy into a stent as compared tothe forming of a stent from a metal alloy that principally includesmolybdenum and rhenium. In one non-limiting composition, the content ofmolybdenum and rhenium and the at least one additional metal in thenovel metal alloy is at least about 90 weight percent. In another and/oralternative non-limiting composition, the content of molybdenum andrhenium and the at least one additional metal in the novel metal alloyis at least about 95 weight percent. In still another and/or alternativenon-limiting composition, the content of molybdenum and rhenium and theat least one additional metal in the novel metal alloy is at least about98 weight percent. In yet another and/or alternative non-limitingcomposition, the content of molybdenum and rhenium and the at least oneadditional metal in the novel metal alloy is at least about 99 weightpercent. In still yet another and/or alternative non-limitingcomposition, the content of molybdenum and rhenium and the at least oneadditional metal in the novel metal alloy is at least about 99.5 weightpercent. In a further one non-limiting composition, the content ofmolybdenum and rhenium and the at least one additional metal in thenovel metal alloy is at least about 99.9 weight percent. In still afurther and/or alternative non-limiting composition, the content ofmolybdenum and rhenium and the at least one additional metal in thenovel metal alloy is at least about 99.95 weight percent. In yet afurther and/or alternative non-limiting composition, the content ofmolybdenum and rhenium and the at least one additional metal in thenovel metal alloy is at least about 99.99 weight percent. As can beappreciated, other weight percentages of the content of molybdenum andrhenium and the at least one additional metal in the novel metal alloycan be used. In one non-limiting composition, the purity level of thenovel metal alloy is such so as to produce a solid solution of a rheniumand molybdenum and the at least one additional metal. A solid solutionor homogeneous solution is defined as a metal alloy that includes two ormore primary metals and the combined weight percent of the primarymetals is at least about 95 weight percent, typically at least about 99weight percent, more typically at least about 99.5 weight percent, evenmore typically at least about 99.8 weight percent, and still even moretypically at least about 99.9 weight percent. A primary metal is a metalcomponent of the metal alloy that is not a metal impurity. A solidsolution of a novel metal alloy that includes rhenium and molybdenum andthe at least one additional metal of titanium, yttrium and/or zirconiumas the primary metals is an alloy that includes at least about 95-99weight percent rhenium and molybdenum and the at least one additionalmetal. It is believed that a purity level of less than 95 weight percentmolybdenum and rhenium and the at least one additional metal adverselyaffects one or more physical properties of the metal alloy that areuseful or desired in forming and/or using a stent. In one embodiment ofthe invention, the rhenium content of the novel metal alloy inaccordance with the present invention is at least about 40 weightpercent. In one non-limiting composition, the rhenium content of thenovel metal alloy is at least about 45 weight percent. In still anotherand/or alternative non-limiting composition, the rhenium content of thenovel metal alloy is about 45-50 weight percent. In yet another and/oralternative non-limiting composition, the rhenium content of the novelmetal alloy is about 47-48 weight percent. In still yet another and/oralternative non-limiting composition, the rhenium content of the novelmetal alloy is about 47.6-49.5 weight percent. As can be appreciated,other weight percentages of the rhenium content of the novel metal alloycan be used. In another and/or alternative embodiment of the invention,the molybdenum content of the novel metal alloy is at least about 40weight percent. In one non-limiting composition, the molybdenum contentof the novel metal alloy is at least about 45 weight percent. In anotherand/or alternative non-limiting composition, the molybdenum content ofthe novel metal alloy is at least about 50 weight percent. In stillanother and/or alternative non-limiting composition, the molybdenumcontent of the novel metal alloy is about 50-60 percent. In yet anotherand/or alternative non-limiting composition, the molybdenum content ofthe novel metal alloy is about 50-56 weight percent. As can beappreciated, other weight percentages of the molybdenum content of thenovel metal alloy can be used. The combined content of titanium, yttriumand zirconium in the novel metal alloy is less than about 5 weightpercent, typically no more than about 1 weight percent, and moretypically no more than about 0.5 weight percent. A higher weight percentcontent of titanium, yttrium and/or zirconium in the novel metal alloycan begin to adversely effect the brittleness of the novel metal alloy.When titanium is included in the novel metal alloy, the titanium contentis typically less than about 1 weight percent, more typically less thanabout 0.6 weight percent, even more typically about 0.05-0.5 weightpercent, still even more typically about 0.1-0.5 weight percent. As canbe appreciated, other weight percentages of the titanium content of thenovel metal alloy can be used. When zirconium is included in the novelmetal alloy, the zirconium content is typically less than about 0.5weight percent, more typically less than about 0.3 weight percent, evenmore typically about 0.01-0.25 weight percent, still even more typicallyabout 0.05-0.25 weight percent. As can be appreciated, other weightpercentages of the zirconium content of the novel metal alloy can beused. When titanium and zirconium are included in the novel metal alloy,the weight ratio of titanium to zirconium is about 1-10:1, typicallyabout 1.5-5:1, and more typically about 1.75-2.5:1. When yttrium isincluded in the novel metal alloy, the yttrium content is typically lessthan about 0.3 weight percent, more typically less than about 0.2 weightpercent, and even more typically about 0.01-0.1 weight percent. As canbe appreciated, other weight percentages of the yttrium content of thenovel metal alloy can be used. The inclusion of titanium, yttrium and/orzirconium in the novel metal alloy is believed to result in a reductionof oxygen trapped in the solid solution of the novel metal alloy. Thereduction of trapped oxygen enables the formation of a smaller grainsize in the novel metal alloy and/or an increase in the ductility of thenovel metal alloy. The reduction of trapped oxygen in the novel metalalloy can also increase the yield strength of the novel metal alloy ascompared to alloys of only molybdenum and rhenium (i.e., 2-10%increase). The inclusion of titanium, yttrium and/or zirconium in thenovel metal alloy is also believed to cause a reduction in the trappedfree carbon in the novel metal alloy. The inclusion of titanium, yttriumand/or zirconium in the novel metal alloy is believed to form carbideswith the free carbon in the novel metal alloy. This carbide formation isalso believed to improve the ductility of the novel metal alloy and toalso reduce the incidence of cracking during the forming of the metalalloy into a medical device (e.g., stent, etc.). As such, the novelmetal alloy exhibits increased tensile elongation as compared to alloysof only molybdenum and rhenium (i.e., 1-8% increase). The inclusion oftitanium, yttrium and/or zirconium in the novel metal alloy is alsobelieved to cause a reduction in the trapped free nitrogen in the novelmetal alloy. The inclusion of titanium, yttrium and/or zirconium in thenovel metal alloy is believed to form carbo-nitrides with the freecarbon and free nitrogen in the novel metal alloy. This carbo-nitrideformation is also believed to improve the ductility of the novel metalalloy and to also reduce the incidence of cracking during the forming ofthe metal alloy into a medical device (e.g., stent, etc.). As such, thenovel metal alloy exhibits increased tensile elongation as compared toalloys of only molybdenum and rhenium (i.e., 1-8% increase). Thereduction of the amount of free carbon, oxygen and/or nitrogen in thenovel metal alloy is also believed to increase the density of the novelmetal alloy (i.e., 1-5% increase). The formation of carbides,carbo-nitrides, and/or oxides in the novel metal alloy results in theformation of dispersed second phase particles in the novel metal alloy,thereby facilitating in the formation of small grain sizes in the metalalloy.

In still another and/or alternative non-limiting aspect of the presentinvention, the novel metal alloy includes less than about 5 weightpercent other metals and/or impurities. A high purity level of the novelmetal alloy results in the formation of a more homogeneous alloy, whichin turn results in a more uniform density throughout the novel metalalloy, and also results in the desired yield and ultimate tensilestrengths of the novel metal alloy. The density of the novel metal alloyis generally at least about 12.5 gm/cc, typically at least about 13.5gm/cc, and more typically about 13.5-13.9 gm/cc. This substantiallyuniform high density of the novel metal alloy significantly improves theradiopacity of the novel metal alloy. In one non-limiting composition,the novel metal alloy includes less than about 1 weight percent othermetals and/or impurities. In another and/or alternative non-limitingcomposition, the novel metal alloy includes less than about 0.5 weightpercent other metals and/or impurities. In still another and/oralternative non-limiting composition, the novel metal alloy includesless than about 0.4 weight percent other metals and/or impurities. Inyet another and/or alternative non-limiting composition, the novel metalalloy includes less than about 0.2 weight percent other metals and/orimpurities. In still yet another and/or alternative non-limitingcomposition, the novel metal alloy includes less than about 0.1 weightpercent other metals and/or impurities. In a further and/or alternativenon-limiting composition, the novel metal alloy includes less than about0.05 weight percent other metals and/or impurities. In still a furtherand/or alternative non-limiting composition, the novel metal alloyincludes less than about 0.02 weight percent other metals and/orimpurities. In yet a further and/or alternative non-limitingcomposition, the novel metal alloy includes less than about 0.01 weightpercent other metals and/or impurities. As can be appreciated, otherweight percentages of the amount of other metals and/or impurities inthe novel metal alloy can exist.

In yet another and/or alternative non-limiting aspect of the presentinvention, the novel metal alloy includes a certain amount of carbon andoxygen. These two elements have been found to affect the formingproperties and brittleness of the novel metal alloy. The controlledatomic ratio of carbon and oxygen in the novel metal alloy also can beused to minimize the tendency of the novel metal alloy to formmicro-cracks during the forming of the novel alloy into a stent, and/orduring the expansion of the stent in a body passageway. In onenon-limiting embodiment of the invention, the novel metal alloy includesup to about 200 ppm carbon and up to about 150 ppm oxygen. Higher carbonand oxygen contents in the novel metal alloy are believed to adverselyaffect one or more physical properties of the metal alloy that areuseful or desired in forming and/or using a stent. In one non-limitingformulation, the novel metal alloy includes up to about 150 ppm carbon.In still another and/or alternative non-limiting formulation, the novelmetal alloy includes up to about 100 ppm carbon. In yet another and/oralternative non-limiting formulation, the novel metal alloy includesless than about 50 ppm carbon. In still yet another and/or alternativenon-limiting formulation, the novel metal alloy includes up to about 100ppm oxygen. In a further and/or alternative non-limiting formulation,the novel metal alloy includes up to about 75 ppm oxygen. In still afurther and/or alternative non-limiting formulation, the novel metalalloy includes up to about 50 ppm oxygen. In yet a further and/oralternative non-limiting formulation, the novel metal alloy includes upto about 30 ppm oxygen. In still yet a further and/or alternativenon-limiting formulation, the novel metal alloy includes less than about20 ppm oxygen. In yet a further and/or alternative non-limitingformulation, the novel metal alloy includes less than about 10 ppmoxygen. As can be appreciated, other amounts of carbon and/or oxygen inthe novel metal alloy can exist. In another and/or alternativenon-limiting embodiment of the invention, the carbon to oxygen atomicratio in the novel metal alloy is generally at least about 2:1 (i.e.,weight ratio of about 1.5:1). The control of the atomic ratio of carbonto oxygen in the novel metal alloy allows for the redistribution ofoxygen in the metal alloy so as to minimize the tendency ofmicro-cracking in the novel metal alloy during the forming of the novelalloy into a medical device, and/or during the use and/or expansion ofthe medical device in a body passageway. When the carbon to oxygenatomic ratio falls below 2-2.5:1 (i.e., weight ratio of about1.5-1.88:1), the degree of elongation of the novel metal alloy decreasesand the incidence of micro-cracking increases, thus adversely affectingone or more physical properties of the metal alloy that are useful ordesired in forming and/or using the stent. In one non-limitingformulation, the carbon to oxygen atomic ratio in the novel metal alloyis generally at least about 2.5:1 (i.e., weight ratio of about 1.88:1).In another and/or alternative non-limiting formulation, the carbon tooxygen atomic ratio in the novel metal alloy is generally at least about3:1 (i.e., weight ratio of about 2.25:1). In still another and/oralternative non-limiting formulation, the carbon to oxygen atomic ratioin the novel metal alloy is generally at least about 4:1 (i.e., weightratio of about 3:1). In yet another and/or alternative non-limitingformulation, the carbon to oxygen atomic ratio in the novel metal alloyis generally at least about 5:1 (i.e., weight ratio of about 3.75:1). Instill yet another and/or alternative non-limiting formulation, thecarbon to oxygen atomic ratio in the novel metal alloy is generallyabout 2.5-50:1 (i.e., weight ratio of about 1.88-37.54:1). In a furtherand/or alternative non-limiting formulation, the carbon to oxygen atomicratio in the novel metal alloy is generally about 2.5-20:1 (i.e., weightratio of about 1.88-15:1). In still a further and/or alternativenon-limiting formulation, the carbon to oxygen atomic ratio in the novelmetal alloy is generally about 2.5-10:1 (i.e., weight ratio of about1.88-7.5:1). In yet a further and/or alternative non-limitingformulation, the carbon to oxygen atomic ratio in the novel metal alloyis generally about 2.5-5:1 (i.e., weight ratio of about 1.88-3.75:1). Ascan be appreciated, other atomic ratios of the carbon to oxygen in thenovel metal alloy can be used.

In still yet another and/or alternative non-limiting aspect of thepresent invention, the novel metal alloy includes a controlled amount ofnitrogen. Large amounts of nitrogen in the novel metal alloy canadversely affect the ductility of the novel metal alloy. This can inturn adversely affect the elongation properties of the novel metalalloy. A nitrogen content in the novel metal alloy of over 20 ppm canbegin to cause the ductility of the novel metal alloy to unacceptablydecrease, thus adversely affect one or more physical properties of themetal alloy that are useful or desired in forming and/or using thestent. In one non-limiting embodiment of the invention, the novel metalalloy includes less than about 30 ppm nitrogen. In one non-limitingformulation, the novel metal alloy includes less than about 25 ppmnitrogen. In still another and/or alternative non-limiting formulation,the novel metal alloy includes less than about 10 ppm nitrogen. In yetanother and/or alternative non-limiting formulation, the novel metalalloy includes less than about 5 ppm nitrogen. As can be appreciated,other amounts of nitrogen in the novel metal alloy can exist.

In a further and/or alternative non-limiting aspect of the presentinvention, the novel metal alloy has several physical properties thatpositively affect the stent when at least partially formed of the metalalloy. In one non-limiting embodiment of the invention, the averagehardness of the metal alloy tube used to form the stent is generally atleast about 60 (HRC) at 77° F. In one non-limiting aspect of thisembodiment, the average hardness of the metal alloy tube used to formthe stent is generally at least about 70 (HRC) at 77° F., and typicallyabout 80-100 (HRC) at 77° F. In another and/or alternative non-limitingembodiment of the invention, the average ultimate tensile strength ofthe metal alloy used to form the stent is generally at least about 90UTS (ksi). In non-limiting aspect of this embodiment, the averageultimate tensile strength of the metal alloy used to form the stent isgenerally at least about 100 UTS (ksi), and typically about 100-150 UTS(ksi). In still another and/or alternative non-limiting embodiment ofthe invention, the average yield strength of the metal alloy used toform the stent is at least about 90 ksi. In one non-limiting aspect ofthis embodiment, the average yield strength of the metal alloy used toform the stent is at least about 110 ksi, and typically about 110-140(ksi). In yet another and/or alternative non-limiting embodiment of theinvention, the average grain size of the metal alloy used to form thestent is greater than 5 ASTM (e.g., ASTM E 112-96). The small grain sizeof the metal alloy enables the stent to have the desired elongation andductility properties that are useful in enabling the stent to be formed,crimped and/or expanded. In one non-limiting aspect of this embodiment,the average grain size of the metal alloy used to form the stent isabout 5.2-10 ASTM, typically about 5.5-9 ASTM, more typically about 6-9ASTM, still more typically about 6-8 ASTM, even more typically about 6-7ASTM, and still even more typically about 6.5-7 ASTM. In still yetanother and/or alternative non-limiting embodiment of the invention, theaverage tensile elongation of the metal alloy used to form the stent isat least about 25%. An average tensile elongation of at least 25% forthe metal alloy is important to enable the stent to be properly expandedwhen positioned in the treatment area of a body passageway. A stent thatdoes not have an average tensile elongation of at least about 25% canform micro-cracks and/or break during the forming, crimping and/orexpansion of the stent. In one non-limiting aspect of this embodiment,the average tensile elongation of the metal alloy used to form the stentis about 28-35%. In another and/or alternative non-limiting aspect ofthis embodiment, the average tensile elongation of the metal alloy usedto form the stent is about 29-35%. The unique combination of the rheniumcontent in the metal alloy in combination with achieving the desiredpurity and composition of the alloy and the desired grain size of themetal alloy results in 1) a stent having the desired high ductility atabout room temperature, 2) a stent having the desired amount of tensileelongation, 3) a homogeneous or solid solution of a metal alloy havinghigh radiopacity, 4) a reduction or prevention of microcrack formationand/or breaking of the metal alloy tube when the metal alloy tube issized and/or cut to form the stent, 5) a reduction or prevention ofmicrocrack formation and/or breaking of the stent when the stent iscrimped onto a balloon and/or other type of medical device for insertioninto a body passageway, 6) a reduction or prevention of microcrackformation and/or breaking of the stent when the stent is bent and/orexpanded in a body passageway, 7) a stent having the desired ultimatetensile strength and yield strength, 8) a stent that can have very thinwall thicknesses and still have the desired radial forces needed toretain the body passageway on an open state when the stent has beenexpanded, and/or 9) a stent that exhibits less recoil when the stent iscrimped onto a delivery system and/or expanded in a body passageway.

Several non-limiting examples of the novel metal alloy in accordancewith the present invention are set forth below: Metal/Wt. % Ex. 1 Ex. 2Ex. 3 C ≦150 ppm ≦150 ppm ≦150 ppm Mo 50-60% 50-60% 50-55% O ≦100 ppm≦100 ppm ≦100 ppm N  ≦40 ppm  ≦40 ppm  ≦40 ppm Re 40-50% 40-50% 45-50%Ti ≦0.5% ≦0.5% ≦0.5% Y ≦0.1% ≦0.1% ≦0.1% Zr ≦0.25%  ≦0.25%  ≦0.25% Metal/Wt. % Ex. 4 Ex. 5 Ex. 6 C ≦150 ppm ≦150 ppm ≦150 ppm Mo   52-55.5%51-58% 50-56% O ≦100 ppm ≦100 ppm ≦100 ppm N  ≦20 ppm  ≦20 ppm  ≦20 ppmRe 44.5-48%   42-49% 44-50% Ti ≦0.5% ≦0.5% ≦0.5% Y ≦0.1% ≦0.1% ≦0.1% Zr≦0.25%  ≦0.25%  ≦0.25% 

In the examples above, the novel metal alloy is principally formed ofrhenium and molybdenum and at least one metal of titanium, yttriumand/or zirconium, and the content of other metals and/or impurities isless than about 0.2 weight percent of the novel metal alloy. In theexamples above, the ratio of carbon to oxygen is at least about 2.5:1,and the average grain size of novel metal alloy is about 6-10 ASTM.

Additional non-limiting examples of the novel metal alloy in accordancewith the present invention are set forth below: Metal/ Wt. % Ex. 7 Ex. 8Ex. 9 Ex. 10 C ≦50 ppm ≦50 ppm ≦50 ppm ≦50 ppm Mo 51-54% 52.5-55.5%52-56% 52.5-55%   O ≦20 ppm ≦20 ppm ≦10 ppm ≦10 ppm N ≦20 ppm ≦20 ppm≦10 ppm ≦10 ppm Re 46-49% 44.5-47.5% 44-48%   45-47.5% Ti ≦0.4% ≦0.4%0.2-0.4% 0.3-0.4% Y ≦0.1% ≦0.1%   0-0.08% 0.005-0.05%  Zr ≦0.2% ≦0.2%  0-0.2%  0.1-0.25% Metal/ Wt. % Ex. 11 Ex. 12 Ex. 13 Ex. 14 C ≦40 ppm≦40 ppm ≦40 ppm ≦40 ppm Mo 50.5-53%   51.5-54%   52-55% 52.5-55%   O ≦15ppm ≦15 ppm ≦15 ppm ≦10 ppm N ≦10 ppm ≦10 ppm ≦10 ppm ≦10 ppm Re  47-49.5%   46-48.5% 45-48%   45-47.5% Ti  0.1-0.35%   0% 0% 0.1-0.3% Y  0% 0.002-0.08%  0% 0% Zr   0%   0% 0.01-0.2%  0.05-0.15% Metal/Wt. %Ex. 15 Ex. 16 C ≦40 ppm ≦40 ppm Mo 52-55% 52.5-55.5% O ≦10 ppm ≦10 ppm N≦10 ppm ≦10 ppm Re 45-49% 44.5-47.5% Ti 0.05-0.4%  0% Y 0.005-0.07% 0.004-0.06%  Zr 0% 0.1-0.2%

In examples 7-16 above, the novel metal alloy is principally formed ofrhenium and molybdenum and at least one metal of titanium, yttriumand/or zirconium, and the content of other metals and/or impurities isless than about 0.1 weight percent of the novel metal alloy, the ratioof carbon to oxygen is about 2.5-10:1, the average grain size of thenovel metal alloy is about 6-9 ASTM, the tensile elongation of the metalalloy is about 25-35%, the average density of the metal alloy is atleast about 13.6 gm/cc, the average yield strength of the metal alloy isat least about 110 (ksi), the average ultimate tensile strength of themetal alloy is about 100-150 UTS (ksi), and the average hardness of themetal alloy is about 80-100 (HRC) at 77° F. In example 10, the weightratio of titanium to zirconium is about 1.5-3:1. In example 14, theweight ratio of titanium to zirconium is about 1.75-2.5:1. In all theother examples, when the alloy includes titanium and zirconium, theweight ratio of titanium to zirconium is about 1-10:1.

In another and/or alternative non-limiting aspect of the presentinvention, the use of the novel metal alloy in the stent can increasethe strength of the stent as compared with stainless steel orchromium-cobalt alloys, thus less quantity of novel metal alloy can beused in the stent to achieve similar strengths as compared to stentsformed of different metals. As such, the resulting stent can be madesmaller and less bulky by use of the novel metal alloy withoutsacrificing the strength and durability of the stent. Such a stent canhave a smaller profile, thus can be inserted in smaller areas, openingsand/or passageways. The novel metal alloy also can increase the radialstrength of the stent. For instance, the thickness of the walls of thestent and/or the wires used to form the stent can be made thinner andachieve a similar or improved radial strength as compared with thickerwalled stents formed of stainless steel or cobalt and chromium alloy.The novel metal alloy also can improve stress-strain properties,bendability and flexibility of the stent, thus increase the life of thestent. For instance, the stent can be used in regions that subject thestent to bending. Due to the improved physical properties of the stentfrom the novel metal alloy, the stent has improved resistance tofracturing in such frequent bending environments. In addition oralternatively, the improved bendability and flexibility of the stent dueto the use of the novel metal alloy can enable the stent to be moreeasily inserted into a body passageway. The novel metal alloy can alsoreduce the degree of recoil during the crimping and/or expansion of thestent. For example, the stent better maintains its crimped form and/orbetter maintains its expanded form after expansion due to the use of thenovel metal alloy. As such, when the stent is to be mounted onto adelivery device when the stent is crimped, the stent better maintainsits smaller profile during the insertion of the stent in a bodypassageway. Also, the stent better maintains its expanded profile afterexpansion so as to facilitate in the success of the stent in thetreatment area. In addition to the improved physical properties of thestent by use of the novel metal alloy, the novel metal alloy hasimproved radiopaque properties as compared to standard materials such asstainless steel or cobalt-chromium alloy, thus reducing or eliminatingthe need for using marker materials on the stent. For instance, thenovel metal alloy is at least about 10-20% more radiopaque thanstainless steel or cobalt-chromium alloy. Specifically, the novel metalalloy can be at least about 33% more radiopaque than cobalt-chromiumalloy and at least about 41.5% more radiopaque than stainless steel.

In still yet another and/or alternative non-limiting aspect of thepresent invention, the stent that is at least partially formed from thenovel metal alloy can be formed by a variety of manufacturingtechniques. In one non-limiting embodiment of the invention, the stentcan be formed from a rod or tube of the novel metal alloy. If a solidrod of the novel metal alloy is formed, the rod can be drilled (e.g.,gun drilled, EDM, etc.) to form a cavity or passageway partially orfully through the rod. The rod or tube can be cleaned, polished,annealed, drawn, etc. to obtain the desired diameter and/or wallthickness of the metal tube. After the metal tube has been formed to thedesired diameter and wall thickness, the metal tube can be formed into astent by a process such as, but not limited to, laser cutting, etching,etc. After the stent has been formed, the stent can be cleaned,polished, sterilized, etc. for final processing of the stent.

In another and/or alternative non-limiting aspect of the invention, thestent can include a bistable construction. In such a design, the stenthas two or more stable configurations, including a first stableconfiguration with a first cross-sectional shape and a second stableconfiguration with a second cross-sectional shape. All or a portion ofthe stent can include the bistable construction. The bistableconstruction can result in a generally uniform change in shape of thestent, or one portion of the stent can change into one or moreconfigurations and one or more other portions of the stent can changeinto one or more other configurations.

In still another and/or alternative aspect of the invention, the stentcan be an expandable device that can be expanded by use of a some otherdevice (e.g., balloon, etc.) and/or is self expanding. The expandablestent can be at least partially fabricated from a material that has noor substantially no shape memory characteristics and/or can be at leastpartially fabricated from a material having shape-memorycharacteristics.

In one non-limiting application of the present invention, there isprovided a medical device in the form of a stent that is at leastpartially formed of a novel metal alloy. The novel metal alloy impartsone or more improved physical characteristics to the stent (e.g.,strength, durability, hardness, biostability, bendability, coefficientof friction, radial strength, flexibility, tensile strength, elongation,longitudinal lengthening, stress-strain properties, improved recoilproperties, radiopacity, heat sensitivity, biocompatibility, etc.). Thenovel metal alloy includes at least about 99 weight percent rhenium andmolybdenum. The stent can have a variety of applications such as, butnot limited to placement into the vascular system, esophagus, trachea,colon, biliary tract, or urinary tract; however, the stent can haveother applications. The stent can have one or more body members, whereineach body member includes first and second ends and a wall surfacedisposed between the first and second ends. Each body member can have afirst cross-sectional area which permits delivery of the body memberinto a body passageway, and a second, expanded cross-sectional area. Theexpansion of the stent body member can be accomplished in a variety ofmanners. Typically, the body member is expanded to its secondcross-sectional area by a radially, outwardly extending force applied atleast partially from the interior region of the body member (e.g., byuse of a balloon, etc.); however, this is not required. When the secondcross-sectional area is variable, the second cross-sectional area istypically dependent upon the amount of radially outward force applied tothe body member. The stent can be designed such that the body memberexpands while retaining the original length of the body member; however,this is not required. The body member can have a first cross-sectionalshape that is generally circular so as to form a substantially tubularbody member; however, the body member can have other cross-sectionalshapes. When the stent includes two of more body members, the two ofmore body members can be connected together by at least one connectormember. The stent can include rounded, smooth and/or blunt surfaces tominimize and/or prevent damage to a body passageway as the stent isinserted into a body passageway and/or expanded in a body passageway;however, this is not required. The stent can be treated with gamma, betaand/or e-beam radiation, and/or otherwise sterilized; however, this isnot required. The stent can have multiple sections. The sections of thestent can have a uniform architectural configuration, or can havediffering architectural configurations. Each of the sections of thestent can be formed of a single part or formed of multiple parts whichhave been attached. When a section is formed of multiple parts,typically the section is formed into one continuous piece; however, thisis not required. One or more portions of the stent can be coated withone or more biological agents. The one or more biological agents, whenused, can be coated so as to be controllably or uncontrollably releasedfrom the stent.

The use of the novel metal alloy to form all or a portion of a stentresults in several advantages over stent formed from other materials.These advantages include, but are not limited to,

-   -   The novel metal alloy has increased strength as compared with        stainless steel or chromium-cobalt alloys, thus less quantity of        novel metal alloy can be used in the stent to achieve similar        strengths as compared to stents formed of different metals. As        such, the resulting stent can be made smaller and less bulky by        use of the novel metal alloy without sacrificing the strength        and durability of the stent. The stent can also have a smaller        profile, thus can be inserted into smaller areas, openings        and/or passageways. The increased strength of the novel metal        alloy also results in the increased radial strength of the        stent. For instance, the thickness of the walls of the stent        and/or the wires used to form the stent can be made thinner and        achieve a similar or improved radial strength as compared with        thicker walled stents formed of stainless steel or cobalt and        chromium alloy.    -   The novel metal alloy has improved stress-strain properties,        bendability properties, elongation properties and/or flexibility        properties of the stent as compared with stainless steel or        chromium-cobalt alloys, thus resulting in an increased life for        the stent. For instance, the stent can be used in regions that        subject the stent to repeated bending. Due to the improved        physical properties of the stent from the novel metal alloy, the        stent has improved resistance to fracturing in such frequent        bending environments. These improved physical properties at        least in part result from the composition of the novel metal        alloy; the grain size of the novel metal alloy; the carbon,        oxygen and nitrogen content of the novel metal alloy; and/or the        carbon/oxygen ratio of the novel metal alloy.    -   The novel metal alloy has a reduced the degree of recoil during        the crimping and/or expansion of the stent as compared with        stainless steel or chromium-cobalt alloys. The stent formed of        the novel metal alloy better maintains its crimped form and/or        better maintains its expanded form after expansion due to the        use of the novel metal alloy. As such, when the stent is to be        mounted onto a delivery device when the stent is crimped, the        stent better maintains its smaller profile during the insertion        of the stent in a body passageway. Also, the stent better        maintains its expanded profile after expansion so as to        facilitate in the success of the stent in the treatment area.    -   The novel metal alloy has improved radiopaque properties as        compared to standard materials such as stainless steel or        cobalt-chromium alloy, thus reducing or eliminating the need for        using marker materials on the stent. For instance, the novel        metal alloy is at least about 10-20% more radiopaque than        stainless steel or cobalt-chromium alloy.    -   The novel metal alloy is less of an irritant to the body than        stainless steel or cobalt-chromium alloy, thus can result in        reduced inflammation, faster healing, increased success rates of        the stent. When the stent is expanded in a body passageway, some        minor damage to the interior of the passageway can occur. When        the body begins to heal such minor damage, the body has less        adverse reaction to the presence of the novel metal alloy than        compared to other metals such as stainless steel or        cobalt-chromium alloy.

One non-limiting object of the present invention is the provision of amedical device that is at least partially formed of a novel metal alloy.

Another and/or alternative non-limiting object of the present inventionis the provision of a medical device having improved procedural successrates.

Still another and/or alternative non-limiting object of the presentinvention is the provision of a medical device that is formed of amaterial that improves the physical properties of the medical device.

Yet another and/or alternative non-limiting object of the presentinvention is the provision of a medical device that is at leastpartially formed of a novel metal alloy that has increased strength andcan also be used as a marker material.

Still yet another and/or alternative non-limiting object of the presentinvention is the provision of a medical device that at least partiallyincludes a novel metal alloy that enables the medical device to beformed with less material without sacrificing the strength of themedical device as compared to prior medical devices.

These and other advantages will become apparent to those skilled in theart upon the reading and following of this description taken togetherwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference may now be made to the drawings, which illustrate variousembodiments that the invention may take in physical form and in certainparts and arrangements of parts wherein:

FIG. 1 is a perspective view of a section of a medical device in theform of an unexpanded stent which permits delivery of the stent into abody passageway; and,

FIG. 2 is a cross-sectional view along line 2-2 of FIG. 1 illustratingthe novel metal alloy material that forms the medical device.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein the showings are for the purposeof illustrating embodiments of the invention only and not for thepurpose of limiting the same, FIGS. 1-2 disclose a medical device in theform of a stent for use in a body passageway. The stent of the presentinvention can be at least partially formed of a novel metal alloy havingimproved physical properties. The novel metal alloy used to at leastpartially form the stent improves one or more properties (e.g.,strength, durability, hardness, biostability, bendability, coefficientof friction, radial strength, flexibility, tensile strength, tensileelongation, longitudinal lengthening, stress-strain properties, improvedrecoil properties, radiopacity, heat sensitivity, biocompatibility,etc.) of such stent. In some instances, the use of the novel metal alloycan reduce the volume, bulk and/or weight of the stent as compared toprior stents made from traditional materials; however, this is notrequired. The one or more materials used to form the stent include oneor more properties which promote the success of the stent.

The stent illustrated in FIGS. 1-2 is designed to be insertable to adiseased area in a body passageway and to expand the diseased area toenable better or proper fluid flow through the body passageway; however,the stent can be used for other or additional reasons. In one specificnon-limiting example, the stent can be used to open an obstructed bloodvessel. Although FIGS. 1-2 illustrate the stent for use in thecardiovascular field, the stent can be used in other medical fields(e.g., orthopedic field, cardiology field, pulmonology field, urologyfield, nephrology field, gastrointerology field, gynecology field,otolaryngology field, etc.). The stent, when used in the cardiovascularfield, can be used to address various medical problems such as, but notlimited to, restenosis, atherosclerosis, atherogenesis, angina, ischemicdisease, congestive heart failure or pulmonary edema associated withacute myocardial infarction, atherosclerosis, thrombosis, controllingblood pressure in hypertension, platelet adhesion, platelet aggregation,smooth muscle cell proliferation, vascular complications, wounds,myocardial infarction, pulmonary thromboembolism, cerebralthromboembolism, thrombophlebitis, thrombocytopenia and/or bleedingdisorders.

The novel metal alloy that at least partially forms the stent includes amajority weight percent of Mo and Re and an additional metal selectedfrom Ti, Y and/or Zr. The novel metal alloy typically forms at least amajority weight percent of the stent; however, this is not required. Asillustrated in FIGS. 1 and 2, the member structures 36 of stent 20 areformed of 98-100% of the novel metal alloy 40. In one non-limiting novelmetal alloy composition, the metal alloy includes about 44-48 weightpercent Re, about 52-56 weight percent Mo, and up to about 0.5 weightpercent Ti, Y and/or Zr. In one non-limiting example, the novel metalalloy is a solid solution that includes about 44.5-47.5 weight percentRe, 52.5-55.5 weight percent Mo, a weight percent of Mo plus Re plus Ti,Y and/or Zr that is at least about 99.9%, 0.3-0.4 weight percent Ti,0.06-0.1 weight percent Zr, 0-0.05 weight percent Y, a weight ratio ofTi:Zr of 1-3:1, less than about 50 ppm carbon, less than about 10 ppmoxygen, less than about 20 ppm nitrogen, a carbon to oxygen atomic ratioof about 2.5-10:1, and no more than about 0.1 weight impurities. Thetensile elongation of the metal alloy is about 27-35%, the averagedensity of the metal alloy is at least about 13.6 gm/cc., the averageyield strength of the metal alloy is at least about 110 (ksi), theaverage ultimate tensile strength of the metal alloy is about 100-150UTS (ksi), and the average hardness of the metal alloy is about 80-100(HRC) at 77° F. The 99.9 weight percent purity of the metal alloy formsa solid or homogenous solution. The unique combination of carbon andoxygen redistributes the oxygen at the grain boundary of the metalalloy, which in turn helps in reducing (defects) in the ultimatelyformed stent. A controlled carbon to oxygen atomic ratio can also beused to obtain a high ductility of the metal alloy which can be measuredin part as tensile elongation. An increase in tensile elongation is animportant attribute when forming the metal alloy into the stent. Thepurity of the metal alloy also results in a substantially uniformdensity throughout the metal alloy. The density of the solid homogeneoussolution of the metal alloy results in the high radiopacity of the metalalloy. The addition of rhenium in the metal alloy improves the ductilityof the molybdenum. The addition of titanium, yttrium and/or zirconiumfacilitates in grain size reduction of the novel metal alloy, improvesductility of the novel metal alloy and/or increases the yield strengthof the novel metal alloy. The solid or homogeneous solution of the metalalloy results in a metal alloy having the desired tensile yield strengthand ultimate tensile strength of the metal alloy. Nitrogen in the novelmetal alloy is an interstitial element that raises the Ductile BrittleTransition Temperature (DBTT). When the DBTT is too high, the novelmetal alloy can become brittle. The maintenance of nitrogen below about20 ppm overcomes this brittleness problem. The combination of thevarious properties of the solid or homogeneous solution of the metalalloy enables the metal alloy to be formed into a stent that hassuperior performance characteristics such as, but not limited torn highradiopacity with thinner and narrower struts and simultaneously having aradial force adequate to retain the vessel lumen fairly open and preventany recoil. The metal alloy can be fabricated from a tubing with anouter diameter as small as about 0.070 inch and with a wall thickness assmall as about 0.002 inch. In one particular design, the average wallthickness after the final processing of the alloy tube is about0.0021-0.00362 inch, and the average concentricity deviation after thefinal processing of the alloy tube is about 1-20%. As can beappreciated, the size values of the processed alloy rod set forth aboveare merely exemplary for using the metal alloy to form a stent for usein the vascular system of a patient. When the metal alloy is used toform other types of stents for use in different regions of a body, thesize values of the final processed metal alloy can be different. Thesolid or homogeneous solution of the metal alloy has the uniquecharacteristics of purity, ductility, grain size, tensile elongation,yield strength and ultimate tensile strength that permits the metalalloy to be fabricated into the stent tubing without creatingmicrocracks that are detrimental to the stent properties.

Referring again to FIGS. 1-2, the stent is an expandable stent that canbe used to at least partially expanding occluded segments of a bodypassageway; however, the stent can have other or additional uses. Forexample, the expandable stent can be used as, but not limited to, 1) asupportive stent placement within a blocked vasculature opened bytransluminal recanalization, which are likely to collapse in the absenceof an internal support; 2) forming a catheter passage throughmediastinal and/or other veins occluded by inoperable cancers; 3)reinforcing a catheter creating intrahepatic communication betweenportal and/or hepatic veins in patients suffering from portalhypertension; 4) a supportive stent placement of narrowing of theesophagus, the intestine, the ureter and/or the urethra; and/or 5) asupportive stent reinforcement of reopened and previously obstructedbile ducts. Accordingly, use of the term “stent” encompasses theforegoing or other usages within various types of body passageways, andalso encompasses use for expanding a body passageway. The stent can beimplanted or applied in a body passageway by techniques such as, but notlimited to, balloon delivery, sheath catheter delivery, etc.

As shown in FIG. 1, the stent 20 includes at least one body member 30having a first end 32, a second end 34, and member structures 36disposed between the first and second ends. The body member is typicallytubular shaped; however, it can be appreciated that the stent can have avariety of shapes and/or configurations. As can also be appreciated, thestent can be formed of one body member of a plurality of body membersthat are connected together. Body member 30 has a first diameter whichpermits delivery of the body member into a body passageway. The firstdiameter of the body member is illustrated as substantially constantalong the longitudinal length of the body member. As can be appreciated,the body member can have a varying first diameter along at least aportion of the longitudinal length of the body member. The body memberalso has a second expanded diameter, not shown. The second diametertypically varies in size; however, the second diameter can benon-variable. The stent can be expanded in a variety of ways such as bya balloon or be self expanding. A balloon expandable stent is typicallypre-mounted or crimped onto an angioplasty balloon catheter. The ballooncatheter is then positioned into the patient via a guide wire. Once thestent is properly positioned, the balloon catheter is inflated to theappropriate pressure for stent expansion. After the stent has beenexpanded, the balloon catheter is deflated and withdrawn, leaving thestent deployed at the treatment site. The novel metal alloy that is usedto at least partially form the stent has very little recoil, thus oncethe stent is expanded, the stent substantially retains its expandedshape.

One or more surfaces of the stent can be treated so as to have generallysmooth surfaces. Generally, the ends are treated by filing, buffing,polishing, grinding, coating, and/or the like; however, this is notrequired. As a result, sharp edges, pointed surfaces and the like aresubstantially eliminated from the end section of the stent. Typicallymost, if not all, the ends of the stent are treated to have smoothsurfaces. The smooth surfaces of the ends reduce damage to surroundingtissue as the stent is positioned in and/or expanded in a bodypassageway. One or more portions of the stent can include one or morebiological agents.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained, andsince certain changes may be made in the constructions set forth withoutdeparting from the spirit and scope of the invention, it is intendedthat all matter contained in the above description and shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense. The invention has been described with reference topreferred and alternate embodiments. Modifications and alterations willbecome apparent to those skilled in the art upon reading andunderstanding the detailed discussion of the invention provided herein.This invention is intended to include all such modifications andalterations insofar as they come within the scope of the presentinvention. It is also to be understood that the following claims areintended to cover all of the generic and specific features of theinvention herein described and all statements of the scope of theinvention, which, as a matter of language, might be said to falltherebetween.

1. A stent that is at least partially formed of a metal alloy whichimproves the strength and ductility of the stent, said metal alloyincluding at least about 99.9 weight percent of a solid solution of atleast three metals, said metal alloy includes a plurality of secondphase particles, said second phase particles including carbides,carbo-nitrides, oxides or mixtures thereof, said metal alloy includingcarbon and oxygen and having a carbon to oxygen atomic ratio of at leastabout 2.5:1.
 2. The stent as defined in claim 1, wherein said metalalloy including at least about 99.95 weight percent of a solid solutionof at least three metals.
 3. The stent as defined in claim 1, whereinsaid metal alloy has an average yield strength of at least about 110 ksiand an average ultimate tensile strength of at least about 100 ksi. 4.The stent as defined in claim 2, wherein said metal alloy has an averageyield strength of at least about 110 ksi and an average ultimate tensilestrength of at least about 100 ksi.
 5. The stent as defined in claim 1,wherein said metal alloy has an average grain size of over 5 ASTM. 6.The stent as defined in claim 4, wherein said metal alloy has an averagegrain size of over 5 ASTM.
 7. The stent as defined in claim 1, whereinsaid metal alloy has an average tensile elongation of at least about25%.
 8. The stent as defined in claim 6, wherein said metal alloy has anaverage tensile elongation of at least about 25%.
 9. The stent asdefined in claim 1, wherein said metal alloy has a nitrogen content ofless than about 20 ppm, a carbon content of less than about 150 ppm, andan oxygen content of less than about 50 ppm.
 10. The stent as defined inclaim 1, wherein said metal alloy has a nitrogen content of less thanabout 20 ppm, a carbon content of less than about 150 ppm, and an oxygencontent of less than about 50 ppm.
 11. The stent as defined in claim 1,wherein said metal alloy has an average density of at least 13.5 gm/cc.12. The stent as defined in claim 10, wherein said metal alloy has anaverage density of at least 13.5 gm/cc.
 13. The stent as defined inclaim 1, wherein said metal alloy includes about 46-49 weight percentrhenium, about 51-54 weight percent molybdenum, and about 0.02-0.5weight percent additional metal, said additional metal including a metalselected from the group consisting of titanium, yttrium, zirconium, ormixtures thereof.
 14. The stent as defined in claim 13, wherein saidmetal alloy includes about 46-49 weight percent rhenium, about 51-54weight percent molybdenum, and about 0.02-0.5 weight percent additionalmetal, said additional metal including a metal selected from the groupconsisting of titanium, yttrium, zirconium, or mixtures thereof.
 15. Astent that is at least partially formed of a metal alloy which improvesthe strength and ductility of the stent, said metal alloy including atleast about 95 weight percent of a solid solution of at least threemetals, said metal alloy includes a plurality of second phase particles,said second phase particles including carbides, carbo-nitrides, oxidesor mixtures thereof, said metal alloy including carbon and oxygen andhaving a carbon to oxygen atomic ratio of at least about 2.5:1, saidmetal alloy having an average yield strength of at least about 110 ksiand an average ultimate tensile strength of at least about 100 ksi, saidmetal alloy having an average grain size of over 5 ASTM, said metalalloy having an average tensile elongation of at least about 25%. 16.The stent as defined in claim 15, wherein said metal alloy includes atleast about 99 weight percent of a solid solution of at least threemetals.
 17. The stent as defined in claim 15, wherein said metal alloyincludes carbon and oxygen and having a carbon to oxygen atomic ratio ofabout 2.5-10:1.
 18. The stent as defined in claim 16, wherein said metalalloy including carbon and oxygen and having a carbon to oxygen atomicratio of about 2.5-10:1.
 19. The stent as defined in claim 15, whereinsaid metal alloy has a nitrogen content of less than about 20 ppm, acarbon content of less than about 150 ppm, and an oxygen content of lessthan about 50 ppm.
 20. The stent as defined in claim 18, wherein saidmetal alloy has a nitrogen content of less than about 20 ppm, a carboncontent of less than about 150 ppm, and an oxygen content of less thanabout 50 ppm.
 21. The stent as defined in claim 15, wherein said metalalloy has an average density of at least 13.5 gm/cc.
 22. The stent asdefined in claim 20, wherein said metal alloy has an average density ofat least 13.5 gm/cc.
 23. The stent as defined in claim 15, wherein saidmetal alloy includes about 46-49 weight percent rhenium, about 51-54weight percent molybdenum, and about 0.02-0.5 weight percent additionalmetal, said additional metal including a metal selected from the groupconsisting of titanium, yttrium, zirconium, or mixtures thereof.
 24. Thestent as defined in claim 22, wherein said metal alloy includes about46-49 weight percent rhenium, about 51-54 weight percent molybdenum, andabout 0.02-0.5 weight percent additional metal, said additional metalincluding a metal selected from the group consisting of titanium,yttrium, zirconium, or mixtures thereof.
 25. A stent that is at leastpartially formed of a metal alloy which improves the strength andductility of the stent, said metal alloy including at least about 95weight percent of a solid solution of rhenium, molybdenum and anadditional metal, said metal alloy including at least about 40 weightpercent rhenium and at least about 50 weight percent molybdenum and upto about 0.5 weight percent of said additional metal, said additionalmetal including a metal selected from the group consisting of titanium,yttrium, zirconium, or mixtures thereof.
 26. The stent as defined inclaim 25, wherein said metal alloy includes at least about 99.9 weightpercent rhenium and molybdenum, said rhenium content about 44-48 weightpercent of said alloy.
 27. The stent as defined in claim 25, whereinsaid carbon content of said metal alloy is less than about 100 ppm andsaid oxygen content of said metal alloy is less than about 50 ppm. 28.The stent as defined in claim 26, wherein said carbon content of saidmetal alloy is less than about 100 ppm and said oxygen content of saidmetal alloy is less than about 50 ppm.
 29. The stent as defined in claim27, wherein said carbon content of said metal alloy is less than about50 ppm and said oxygen content of said metal alloy is less than about 10ppm.
 30. The stent as defined in claim 28, wherein said carbon contentof said metal alloy is less than about 50 ppm and said oxygen content ofsaid metal alloy is less than about 10 ppm.
 31. The stent as defined inclaim 25, wherein said ratio of carbon to oxygen in said metal alloy isat least about 2.5:1.
 32. The stent as defined in claim 30, wherein saidratio of carbon to oxygen in said metal alloy is at least about 2.5:1.33. The stent as defined in claim 25, wherein said metal alloy includesnitrogen, said nitrogen content of said metal alloy is less than about20 ppm.
 34. The stent as defined in claim 32, wherein said metal alloyincludes nitrogen, said nitrogen content of said metal alloy is lessthan about 20 ppm.
 35. The stent as defined in claim 25, wherein saidmetal alloy has an average grain size of greater than about 5 ASTM. 36.The stent as defined in claim 34, wherein said metal alloy has anaverage grain size of greater than about 5 ASTM.
 37. The stent asdefined in claim 35, wherein said metal alloy has an average grain sizeof about 6-9 ASTM.
 38. The stent as defined in claim 36, wherein saidmetal alloy has an average grain size of about 6-9 ASTM.
 39. The stentas defined in claim 25, wherein said metal alloy has an average tensileelongation of at least about 25%.
 40. The stent as defined in claim 38,wherein said metal alloy has an average tensile elongation of at leastabout 25%.
 41. The stent as defined in claim 25, wherein said metalalloy constitutes at least about 80 weight percent of said stent. 42.The stent as defined in claim 40, wherein said metal alloy constitutesat least about 80 weight percent of said stent.
 43. The stent as definedin claim 25, wherein said metal alloy includes titanium and zirconium,said titanium and zirconium having a weight ratio of about 1.2-5:1. 44.The stent as defined in claim 42, wherein said metal alloy includestitanium and zirconium, said titanium and zirconium having a weightratio of about 1.2-5:1.
 45. The stent as defined in claim 43, whereinsaid metal alloy includes titanium and zirconium, said titanium andzirconium having a weight ratio of about 1.5-3:1.
 46. The stent asdefined in claim 44, wherein said metal alloy includes titanium andzirconium, said titanium and zirconium having a weight ratio of about1.5-3:1.
 47. The stent as defined in claim 25, wherein said metal alloycomprises by weight percent: C <150 ppm Mo 50-55% O <100 ppm N  <40 ppmRe 44-50% Ti ≦0.5% Y ≦0.1% Zr ≦0.25% 

and has a grain size of about 6-8 ASTM, a carbon to oxygen ratio ofabout 2.5-10:1, an average tensile elongation of about 25-35%, and saidcontent of rhenium plus molybdenum plus metal component is at leastabout 99.9 weight percent.
 48. The stent as defined in claim 46, whereinsaid metal alloy comprises by weight percent: C <150 ppm Mo 50-55% O<100 ppm N  <40 ppm Re 44-50% Ti ≦0.5% Y ≦0.1% Zr ≦0.25% 

and has a grain size of about 6-8 ASTM, a carbon to oxygen ratio ofabout 2.5-10:1, an average tensile elongation of about 25-35%, and saidcontent of rhenium plus molybdenum plus metal component is at leastabout 99.9 weight percent.
 49. The stent as defined in claim 25, whereinsaid metal alloy comprises by weight percent: C <50 ppm Mo 51-54% O <20ppm N <20 ppm Re 46-49% Ti ≦0.4% Y ≦0.1% Zr ≦0.2%

and has a grain size of about 6-8 ASTM, a carbon to oxygen ratio ofabout 2.5-10:1, an average tensile elongation of about 25-35%, and saidcontent of rhenium plus molybdenum plus metal component is at leastabout 99.9 weight percent.
 50. The stent as defined in claim 46, whereinsaid metal alloy comprises by weight percent: C <50 ppm Mo 51-54% O <20ppm N <20 ppm Re 46-49% Ti ≦0.4% Y ≦0.1% Zr ≦0.2%

and has a grain size of about 6-8 ASTM, a carbon to oxygen ratio ofabout 2.5-10:1, an average tensile elongation of about 25-35%, and saidcontent of rhenium plus molybdenum plus metal component is at leastabout 99.9 weight percent.
 51. The stent as defined in claim 25, whereinsaid metal alloy comprises by weight percent: C <50 ppm Mo 52.5-55.5% O<20 ppm N <20 ppm Re 44.5-47.5% Ti ≦0.4% Y ≦0.1% Zr ≦0.2%

and has a grain size of about 6-8 ASTM, a carbon to oxygen ratio ofabout 2.5-10:1, an average tensile elongation of about 25-35%, and saidcontent of rhenium plus molybdenum plus metal component is at leastabout 99.9 weight percent.
 52. The stent as defined in claim 46, whereinsaid metal alloy comprises by weight percent: C <50 ppm Mo 52.5-55.5% O<20 ppm N <20 ppm Re 44.5-47.5% Ti ≦0.4% Y ≦0.1% Zr ≦0.2%

and has a grain size of about 6-8 ASTM, a carbon to oxygen ratio ofabout 2.5-10:1, an average tensile elongation of about 25-35%, and saidcontent of rhenium plus molybdenum plus metal component is at leastabout 99.9 weight percent.
 53. The stent as defined in claim 25, whereinsaid metal alloy comprises by weight percent: C <50 ppm Mo 52-56% O <10ppm N <10 ppm Re 44-48% Ti 0.2-0.4% Y   0-0.08% Zr   0-0.2%

and has a grain size of about 6-8 ASTM, a carbon to oxygen ratio ofabout 2.5-10:1, an average tensile elongation of about 25-35%, saidcontent of rhenium plus molybdenum plus metal component is at leastabout 99.9 weight percent, said average yield strength at least about110 ksi.
 54. The stent as defined in claim 46, wherein said metal alloycomprises by weight percent: C <50 ppm Mo 52-56% O <10 ppm N <10 ppm Re44-48% Ti 0.2-0.4% Y   0-0.08% Zr   0-0.2%

and has a grain size of about 6-8 ASTM, a carbon to oxygen ratio ofabout 2.5-10:1, an average tensile elongation of about 25-35%, saidcontent of rhenium plus molybdenum plus metal component is at leastabout 99.9 weight percent, said average yield strength at least about110 ksi.
 55. The stent as defined in claim 25, wherein said metal alloycomprises by weight percent: C <50 ppm Mo  52.5-55% O <10 ppm N <10 ppmRe   45-47.5% Ti  0.3-0.4% Y 0.005-0.05% Zr  0.1-0.25%

and has a grain size of about 6-8 ASTM, a carbon to oxygen ratio ofabout 2.5-10:1, an average tensile elongation of about 25-35%, saidcontent of rhenium plus molybdenum plus metal component is at leastabout 99.9 weight percent, said average yield strength at least about110 ksi.
 56. The stent as defined in claim 46, wherein said metal alloycomprises by weight percent: C <50 ppm Mo  52.5-55% O <10 ppm N <10 ppmRe   45-47.5% Ti  0.3-0.4% Y 0.005-0.05% Zr  0.1-0.25%

and has a grain size of about 6-8 ASTM, a carbon to oxygen ratio ofabout 2.5-10:1, an average tensile elongation of about 25-35%, saidcontent of rhenium plus molybdenum plus metal component is at leastabout 99.9 weight percent, said average yield strength at least about110 ksi.
 57. A stent that is formed of at least about 80 weight percentof a metal alloy which improves the strength and ductility of the stent,said metal alloy including at least about 99.9 weight percent of a solidsolution of rhenium, molybdenum and an additional metal, said metalalloy including at least and effective amount and up to about 0.5 weightpercent of said additional metal, said additional metal including ametal selected from the group consisting of titanium, yttrium,zirconium, or mixtures thereof, said metal alloy including carbon andoxygen and having a carbon to oxygen ratio of at least about 2.5:1, saidmetal alloy having an average yield strength of at least about 110 ksiand an average ultimate tensile strength of about 100-150 ksi, saidmetal alloy having an average grain size of about 6-9 ASTM, said metalalloy having an average tensile elongation of about 25-35%, said metalalloy having an average density of at least about 13.5 gm/cm, and saidmetal alloy including by weight percent: C ≦50 ppm Mo 52-56% O ≦20 ppm N≦10 ppm Re 44-48% Ti  0-0.4% Y  0-0.08% Zr  0-0.25%


58. The stent as defined in claim 57, wherein said metal alloy comprisesby weight percent: C ≦50 ppm Mo  52.5-55% O ≦10 ppm N ≦10 ppm Re  45-47.5% Ti  0.3-0.4% Y 0.005-0.05% Zr  0.1-0.25%

and a weight ratio of titanium to zirconium is about 1.5-3:1.
 59. Thestent as defined in claim 57, wherein said metal alloy comprises byweight percent: C ≦40 ppm Mo  51-53% O ≦15 ppm N ≦10 ppm Re  47-49% Ti0.1-0.35% Y 0% Zr 0%


60. The stent as defined in claim 57, wherein said metal alloy comprisesby weight percent: C ≦40 ppm Mo  51.5-54% O ≦15 ppm N ≦10 ppm Re  46-48.5% Ti 0% Y 0.002-0.08% Zr 0%


61. The stent as defined in claim 57, wherein said metal alloy comprisesby weight percent: C ≦40 ppm Mo   52-55% O ≦15 ppm N ≦10 ppm Re   45-48%Ti 0% Y 0% Zr 0.01-0.2%


62. The stent as defined in claim 57, wherein said metal alloy comprisesby weight percent: C ≦40 ppm Mo 52.5-55% O ≦10 ppm N ≦10 ppm Re  45-47.5% Ti  0.1-0.3% Y 0% Zr 0.05-0.15%

and a weight ratio of titanium to zirconium is about 1.5-3:1.
 63. Thestent as defined in claim 57, wherein said metal alloy comprises byweight percent: C ≦40 ppm Mo   52-55% O ≦10 ppm N ≦10 ppm Re   45-49% Ti 0.05-0.4% Y 0.005-0.07% Zr 0%


64. The stent as defined in claim 57, wherein said metal alloy comprisesby weight percent: C ≦40 ppm Mo  52.5-55.5% O ≦10 ppm N ≦10 ppm Re 44.5-47.5% Ti 0% Y 0.004-0.06% Zr  0.1-0.2%